chore(skills): sync embedded agentfield-use mirror after #827 (#828)

#827 updated the canonical skills/agentfield-use/SKILL.md without running
scripts/sync-embedded-skills.sh, so TestEmbeddedSkillSyncCheck now fails on
main and leaks a red coverage gate into every PR that merges main.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: AbirAbbas